1. Field of Invention
The present invention relates generally to the field of mobile wireless networks. More particularly, in one exemplary aspect, the present invention is directed to methods and apparatus for initiating or re-initiating a data connection to a base station within advanced cellular networks.
2. Description of Related Technology
Wireless networks such as cellular networks provide network service to mobile devices over a large geographic area via a network of base stations. During normal operation, a mobile device establishes a “connection” to a base station in order to transmit and receive data via the cellular network (e.g., place or receive a voice call, text message, etc.) As the mobile device moves, the mobile device and cellular network perform a variety of mobility management functions to ensure that the mobile device can consistently connect to the optimal base station. For example, during an active connection, the cellular network may initiate a “handover” for active connection from a first base station to a second base station, the latter being more optimized for operation under the then prevailing operational and geographic conditions. Similarly, when a mobile device is “idle” (i.e., registered within a cell, but without active communication) it “camps” on a cell (i.e., monitors the cell of a base station) and may intermittently select a new cell to camp on (also commonly referred to as “cell selection” and “cell re-selection”).
Long Term Evolution (LTE) is an emerging cellular network standard designed to, among other things, maximize high-speed data transfer. LTE (and its related progeny LTE-Advanced (LTE-A)) is the latest successor to a cellular technology family that includes Global System for Mobile Communications (GSM), General Packet Radio Service (GPRS), Enhanced Data Rates for GSM Evolution (EDGE), Universal Mobile Telecommunications System (UMTS), High Speed Packet Access (HSPA), etc. LTE is the first of the so-called “fourth generation” (4G) cellular network technologies, which provide an all-Internet Protocol (IP) data delivery paradigm (i.e., 4G technologies are limited to data packet delivery only). Current implementations of LTE do not coordinate base stations; instead, the overall network is a “flattened” IP network (with very minimal hierarchy). The uncoordinated nature of the LTE network infrastructure results in break-before-make type transactions; e.g., LTE handovers are “hard”, in that the mobile device breaks its connection with the first base station before restoring the connection with the second base station. Contrast so-called “soft” handovers, wherein the mobile device connects to the second base station before breaking the connection with the first base station.
Current implementations of LTE cellular networks handle cell selection, cell re-selection, and handover on the basis of received signal strength. Received signal strength is a measurement of the signal power as received at the mobile device. Historically, received signal strength was a computationally efficient metric for a mobile device to ascertain the relative quality of signals received from multiple base stations. Traditional cellular technology has accordingly focused largely on maintaining a connection between the mobile device and the cellular network over a noisy radio channel.
However, unlike other cellular standards, LTE technology is designed to frequently break and re-establish connections with the mobile device. In fact, LTE networks are configured to maximize the overall network performance, irrespective of many other considerations. For example, in some cases, active connections to a mobile device with an LTE network can be abruptly ended so that the base station can provide better service to other devices. Similarly, handovers within LTE may not always be serviced (e.g., where the destination base station is unable to service the handover request due to network congestion, etc.). LTE networks can break a connection to a mobile device, even where the mobile device has good reception (e.g., high received signal strength). Consequently, unlike previous cellular network technologies, reception quality may not accurately reflect the quality of service a mobile device can expect from an LTE base station.
As previously indicated, existing LTE mobile devices attempt to establish or re-establish data connections to the base station having the highest received signal strength. Unfortunately, in many situations where a mobile device is dropped from a base station, the base station from which the mobile device was just disconnected is also the base station that has the highest received signal strength. Consequently, LTE mobile devices will attempt to re-establish a data connection to that same base station; however, in many cases, the base station still cannot support the LTE mobile device for any number of possible reasons. This can result in prolonged out-of-service (OOS) periods, where the LTE mobile device cannot connect back to the same (and ostensibly most optimal) base station.
Accordingly, improved solutions are needed for LTE mobile device cell selection, cell re-selection, and handover, ideally which consider a base station's propensity for servicing a data transfer request successfully, in addition to reception quality. More generally, improved methods and apparatus are needed for initiating or re-initiating a data connection to a base station within advanced cellular networks.